A spatial approach to sunlight exposure and clinical depression

Abstract

Background: Evidence from a variety of sources suggests that sunlight exposure may have an independent effect on the incidence of major depression; however this relationship has not been directly tested. This paper aimed to address this gap using GIS, with the added benefit of demonstrating the value of a spatial approach to future epidemiological studies of depression. Methods: Values for depression, sunshine, SES and green space were collected for each CAS ward in England. These CAS wards were then stratified into 16 categories based on socio-economic status (SES) and green space access. Within each category, the correlation between sunshine hours and depression incidence was tested. Results: Sunlight exposure exhibited a significant negative correlation with depression incidence. As sunshine exposure increased, the incidence of depression decreased. Interestingly, this relationship strengthened with reducing SES. Conclusions: Sunlight exposure has a significant effect on the incidence of depression. Poorer climates could also be acting to exacerbate depression inequalities caused by low SES. Future studies making adjustments for age and gender are necessary to solidify these tentative findings.